Surgical drainage unit



FIG. 1 is a perspective view of the surgical drainage unit, showing my new design, the broken line is for illustrative purposes only and forms no part of the claimed design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left side elevational view thereof, the right side elevational view being identical thereto;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a bottom plan view thereof; and

FIG. 6 is a top plan view thereof. 

The ornamental design for a surgical drainage unit, as shown and described. 